Frogs provide data on wetland health

Researchers have been monitoring frog song along the Great Lakes for a decade.
A boy holds onto a leopard frog in Superior. (Jed Carlson /

Surveying anurans — frogs and toads — in Superior is quick work.

For three minutes, field researchers from the University of Minnesota Duluth's Natural Resources Research Institute listen for the amphibians' song, turning left and right to pinpoint where the sound is coming from and how many are singing. The data they collect, including air and water temperature, weather and vegetation in the area, is pooled with 10 years of information about the flora and fauna along the Great Lakes as part of the Great Lakes Coastal Wetland Monitoring Program.

The boots on the ground Thursday, July 2 were UMD graduate student Lisa Brouellette and Jenna Skull, a college senior spending the summer in Duluth. Their mission: Conduct listening sessions at eight different wetland sites in Superior in four hours. Start time was half an hour after sunset, 9:36 p.m., along a railroad track near Loon’s Foot Landing.

Frogs and toads sing in the spring when they're feeling amorous and trying to attract a mate.


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Field technician Lisa Brouellette, left, writes down data as fellow technician Jenna Skull checks GPS coordinates while surveying frogs along railroad tracks near Loon's Foot Landing in Superior Thursday, July 2. The survey involves listening for the frogs' song and pinpointing how many are singing. (Maria Lockwood /

The frogs, however, were keeping to themselves. A lone green frog sounded off along the railroad tracks. Although the pop of an occasional firework and the buzz of mosquitoes came through loud and clear on the pedestrian bridge over the Nemadji River, there was not a frog to be heard. The same was true at the fishing pier across East Second Street from Kwik Trip. Lightning bugs decorated the grassy area beside the pier with a moving light show, but there wasn't a peep from the frogs.

“Even though there are not frogs, it’s still important data,” Brouellette said. “It helps us study the timing of breeding or habitat qualities that might affect frogs singing.”

At three additional sites along the Nemadji River and two spots on Allouez Bay, a handful of frogs sang out, two to four per site, a few green frogs and a few gray tree frogs.

This is the second year Brouellette has surveyed frogs, toads and birds of Lake Superior coastal wetlands for the Natural Resources Research Institute. It requires patience, a trained ear and a love of the outdoors. There are 14 different species of anuran to hear along the Great Lakes. The work comes with drawbacks, like the clouds of mosquitoes along the Nemadji.

But Brouellett said there are perks, as well.

“The more often you’re out, the more often you get to see cool things,” Brouellette said.

This year, she’s seen river otters near Ashland and an active bald eagle nest containing a chick.


Frog sites are visited three times a year — early, mid and late spring — to catch different species singing during their mating season. The dates are determined by the nighttime temperature, and it can be a narrow window.

“You have things like wood frogs (that) will go crazy for a week or two in the spring and they’re done,” Brouellette said.

The information Brouellette collected offers a comprehensive look at the health of the coastal wetlands.

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Field technician Lisa Brouellette fills out an amphibian monitoring sheet as she listens for frogs' song along the railroad tracks near Loon's Foot Landing Thursday, July 2. (Maria Lockwood /

“The overall goal of the project is to establish long-term monitoring because you only really get a sense of population trends when you have these long-term data sets,” Brouellette said.

Each year, the sites to monitor are chosen randomly from more than 1,000 wetlands rimming the Great Lakes. A network of colleges provide the field technicians and crunch the data, which is aimed at future protection and restoration of the coastal wetlands.

The program is also training the next generation of scientists.


“It’s been really interesting. I just have really been enjoying getting the field experience,” Skull said. “I really like the field stuff; I think that’s the direction I want to go towards when I graduate.”

The program was featured in a 2019 Public Broadcasting System documentary . More information is available online at the Natural Resources Research Institute and Great Lakes Coastal Wetland Monitoring Program websites.

Maria Lockwood covers news in Douglas County, Wisconsin, for the Superior Telegram.
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